TS: Fix a crash when allowJs: true was set

javascript/extractor/src/com/semmle/js/extractor/AutoBuild.java

@@ -578,6 +578,11 @@ public class AutoBuild {
         for (File sourceFile : project.getSourceFiles()) {
           Path sourcePath = sourceFile.toPath();
           if (!files.contains(normalizePath(sourcePath))) continue;
+          if (!FileType.TYPESCRIPT.getExtensions().contains(FileUtil.extension(sourcePath))) {
+            // For the time being, skip non-TypeScript files, even if the TypeScript
+            // compiler can parse them for us.
+            continue;
+          }
           if (!extractedFiles.contains(sourcePath)) {
             typeScriptFiles.add(sourcePath.toFile());
           }

javascript/extractor/src/com/semmle/js/extractor/Main.java

@@ -147,7 +147,8 @@ public class Main {
       List<File> filesToExtract = new ArrayList<>();
       for (File sourceFile : project.getSourceFiles()) {
         if (files.contains(normalizeFile(sourceFile))
-            && !extractedFiles.contains(sourceFile.getAbsoluteFile())) {
+            && !extractedFiles.contains(sourceFile.getAbsoluteFile())
+            && FileType.TYPESCRIPT.getExtensions().contains(FileUtil.extension(sourceFile))) {
           filesToExtract.add(sourceFile);
         }
       }

javascript/ql/test/library-tests/TypeScript/RegressionTests/AllowJs/main.ts

@@ -0,0 +1,2 @@
+import f = require("./tst");
+f("world");

javascript/ql/test/library-tests/TypeScript/RegressionTests/AllowJs/test.expected

@@ -0,0 +1,5 @@
+| main.ts:1:8:1:8 | f | (x: string) => string |
+| main.ts:1:20:1:26 | "./tst" | any |
+| main.ts:2:1:2:1 | f | (x: string) => string |
+| main.ts:2:1:2:10 | f("world") | string |
+| main.ts:2:3:2:9 | "world" | "world" |

javascript/ql/test/library-tests/TypeScript/RegressionTests/AllowJs/test.ql

@@ -0,0 +1,4 @@
+import javascript
+
+from Expr e
+select e, e.getType()

javascript/ql/test/library-tests/TypeScript/RegressionTests/AllowJs/tsconfig.json

@@ -0,0 +1,6 @@
+{
+    "compilerOptions": {
+        "allowJs": true
+    },
+    "include": ["."]
+}

javascript/ql/test/library-tests/TypeScript/RegressionTests/AllowJs/tst.js

@@ -0,0 +1,6 @@
+/**
+ * @param {String} x
+ */
+module.exports = function(x) {
+    return 'Hello ' + x;
+}